The charge pump converter architecture is used in applications where a low cost and a reduced circuit area is desired. In the adjustment of the output voltage, this architecture greatly degrades the energy efficiency, and its use is therefore limited. In addition, this type of architecture is known to generate large ripple in the output voltage, due to the fact that the current provided to the output capacitor is not direct. As a result, this type of architecture generates a lot of noise in the signals generated or processed by the circuits it powers, which reduces its desirability in radio frequency applications.
The boost or buck-boost type of DC-DC conversion architecture is used in applications where an adjustable output voltage is desired. However, this architecture, in addition to also generating a lot of ripple in the output voltage and therefore a lot of noise, involves very high currents. In addition, due to the fact that the control transistors of the circuit operate in the ohmic region, and due to the presence of an inductor in the circuit with its associated parasitic resistance, losses are generated by the Joule effect, which reduces the efficiency of the conversion.
Having an output current which is not direct also means there is no continuous control over the output voltage. This generates problems in the reaction speed of the circuit in addition to the ripple problems, so the circuit then has a narrow frequency range.
A wide frequency range is useful for modulating the output voltage from the DC-DC converter or for responding to rapid variations in the circuit load.